Automatic transmission pump apparatus or pump apparatus

ABSTRACT

The present invention provides a pump apparatus capable of preventing or reducing deterioration of efficiency of a pump. The pump apparatus includes a venturi portion provided on the way along a discharge passage. The venturi portion includes a small diameter portion having a smaller inner diameter than an inner diameter of the discharge passage from a discharge port to the venturi portion and an inner diameter gradually-increasing portion formed in such a manner that an inner diameter thereof gradually increases from the small diameter portion toward a downstream side of the discharge passage. The pump apparatus further includes a control valve configured to receive introduction of hydraulic fluid on an upstream side of the venturi portion and hydraulic fluid in the venturi portion. The control valve is configured to control a flow amount of hydraulic fluid to be supplied into an automatic transmission by switching a flow passage of the hydraulic fluid based on a differential pressure between a pressure on the upstream side of the venturi portion and a pressure in the venturi portion ( 50 ).

TECHNICAL FIELD

The present invention relates to a pump apparatus.

BACKGROUND ART

Conventionally, there has been known a pump apparatus including acontrol valve. The control valve controls a flow amount of hydraulicfluid that the pump apparatus supplies to an apparatus. For example, apump apparatus discussed in PTL 1 generates a differential pressureaccording to the flow amount to be discharged. The control vale controlsthe above-described flow amount by switching a flow passage of thehydraulic fluid based on the above-described differential pressure.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Public Disclosure No. 2010-14074

SUMMARY OF INVENTION Technical Problem

However, the conventional pump apparatus uses an orifice for generatingthe differential pressure. Therefore, efficiency of the pump may bedeteriorated. An object of the present invention is to provide a pumpapparatus capable of preventing or reducing deterioration of theefficiency of the pump.,

Solution To Problem

To achieve the above-described object, one embodiment of the presentinvention includes a venturi portion provided on the way along adischarge passage to generate a differential pressure and having aninner diameter gradually increasing from a small diameter portion towarda downstream side of the discharge passage.

Therefore, the deterioration of the efficiency of the pump can beprevented or reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a configuration of a hydraulic system to which a pumpapparatus according to a first embodiment is applied.

FIG. 2 schematically illustrates a configuration of the pump apparatusaccording to the first embodiment.

FIG. 3 illustrates a partial cross section acquired by cutting a pumphousing according to the first embodiment along a plane perpendicular toa central axis of a diving shaft.

FIG. 4 illustrates a cross section as viewed from a line A-A illustratedin FIG. 3.

FIG. 5 illustrates a venturi forming block according to the firstembodiment as viewed from one side in an axial direction.

An upper diagram of FIG. 6 schematically illustrates a discharge passagearound a venturi portion according to the first embodiment. A lowerdiagram of FIG. 6 illustrates a change in a pressure that is associatedwith each portion illustrated in the upper diagram.

An upper diagram of FIG. 7 schematically illustrates a discharge passagearound an orifice according to a comparative example. A lower diagram ofFIG. 7 illustrates a change in a pressure that is associated with eachportion illustrated in the upper diagram.

FIG. 8 is a graph indicating a relationship between a flow amount and adifferential pressure according to the first embodiment. A solid lineindicates the first embodiment, and an alternate long and short dashline indicates the comparative example.

FIG. 9 illustrates a relationship between a narrower angle and apressure loss rate according to the first embodiment.

An upper diagram of FIG. 10 schematically illustrates a dischargepassage in which a large diameter portion is provided upstream of theventuri portion according to the first embodiment. A lower diagram ofFIG. 10 illustrates a change in a pressure that is associated with eachportion illustrated in the upper diagram.

An upper diagram of FIG. 11 schematically illustrates a dischargepassage including a stepped portion (a rear portion) on a downstreamside of an inner diameter gradually-increasing portion according to thefirst embodiment. A lower diagram of FIG. 11 illustrates a change in apressure that is associated with each portion illustrated in the upperdiagram.

FIG. 12 illustrates a relationship between L/L0, which is a ratio of Lto L0 illustrated in FIG. 11, and the pressure loss rate.

FIG. 13 illustrates a cross section acquired by cutting a venturiforming block according to a second embodiment along a plane passingthrough a central axis of the venturi portion.

FIG. 14 illustrates a pump housing according to a fourth embodiment asviewed from a direction in which the central axis of the driving shaftextends.

FIG. 15 illustrates a cross section as viewed from a line B-Billustrated in FIG. 14.

FIG. 16 schematically illustrates a configuration of a pump apparatusaccording to a sixth embodiment.

FIG. 17 illustrates a partial cross section acquired by cutting a pumphousing according to the sixth embodiment along a plane including thecentral axis of the driving shaft.

DESCRIPTION OF EMBODIMENTS

In the following description, embodiments for implementing a pumpapparatus according to the present invention will be described based onexemplary embodiments illustrated in the drawings.

First Embodiment

First, a configuration will be described. FIG. 1 illustrates aconfiguration of a hydraulic system to which a pump apparatus 1 isapplied. The pump apparatus 1 is mounted on a vehicle of an automobile.The pump apparatus 1 is a hydraulic fluid supply source that supplieshydraulic fluid to another apparatus mounted on the vehicle (anapparatus mounted on a vehicle). The apparatus mounted on the vehicle towhich the pump apparatus 1 supplies the hydraulic fluid is an automatictransmission. The automatic transmission is a stepless transmission, inparticular, a belt-type continuously variable transmission (hereinafterreferred to as a CVT) 10. The hydraulic fluid is ATF (automatictransmission fluid). The pump apparatus 1 is driven by aninternal-combustion engine as a prime mover thereof, and introduces anddischarges the hydraulic fluid from and into an oil pan 100. Forexample, an oil pan of the CVT 10 can be used as the oil pan 100.Various types of valves controlled by a CVT control unit are provided ina control valve of the CVT 10. The hydraulic fluid discharged from thepump apparatus 1 is supplied to each unit (a primary pulley, a secondarypulley, a forward clutch, a reverse brake, a torque converter, alubricant/cooling system, and the like) of the CVT 10 via the controlvalve.

The pump apparatus 1 includes a pump housing 2, a pump element 4, aventuri portion 50, and a control valve 8. The pump housing 2 containsthe pump element 4, the control valve 8, and the venturi portion 50therein. An intake passage 3, a discharge passage 5, a high pressurepassage 6, an intermediate pressure passage 7, and a return passage 9are provided in the pump housing 2 as passages through which thehydraulic fluid flows. The intake passage 3 connects the oil pan 100 andthe pump element 4 to each other. The discharge passage 5 connects thepump element 4 and the CVT 10 to each other. The venturi portion 50 is aconstriction portion provided on the way along the discharge passage 5.The high pressure passage 6 connects one side of the discharge passage 5that is closer to the pump element 4 than the venturi portion 50 is(hereinafter referred to as an upstream side) and the control valve 8 toeach other. The intermediate pressure passage 7 connects the venturiportion 50 and the control valve 8 to each other. The return passage 9connects the control valve 8 and the intake passage 3 (the oil pan 100)to each other. A driving shaft 40 is pivotally supported in the pumphousing 2. The driving shaft 40 is driven by a crank shaft of theinternal-combustion engine. The pump element 4 is rotationally driven bythe driving shaft 40. The pump element 4 introduces the hydraulic fluidtherein from the oil pan 100 via the intake passage 3. The pump element4 discharges the hydraulic fluid to the discharge passage 5, andsupplies the hydraulic fluid to the CVT 10 via the discharge passage 5.A relatively high pressure (hereinafter referred to as a high pressure)on the upstream side of the venturi portion 50 is fed into the controlvalve 8 via the high pressure passage 6. Further, a relatively lowpressure (a pressure around an intermediate level, hereinafter referredto as an intermediate pressure) in the venturi portion 50 is fed intothe control valve 8 via the intermediate pressure passage 7. The controlvalve 8 switches a flow passage of the hydraulic fluid based on adifference (a differential pressure) between the pressure on theupstream side of the venturi portion 50 and the pressure in the venturiportion 50. By this switching, the control valve 8 controls a flowamount of the hydraulic fluid that the pump element 4 supplies to theCVT 10.

FIG. 2 schematically illustrates a configuration of the pump apparatus1. FIG. 2 illustrates a cross section acquired by cutting the pumpelement 4 in a state extracted from the pump housing 2 along a planeperpendicular to a center axis (a rotational axis) O of the drivingshaft 40. FIG. 2 illustrates a partial cross section acquired by cuttingthe control valve 8 along a plane passing through a central axisthereof. FIG. 2 schematically illustrates each of the passages 3 and thelike. A direction in which the hydraulic fluid flows is indicated by anarrowed alternate long and short dash line. FIG. 3 illustrates a partialcross section acquired by cutting the pump housing 2 along the planeperpendicular to the central axis O. FIG. 4 illustrates a cross sectionas viewed from a line A-A illustrated in FIG. 3. Hereinafter, anorthogonal coordinate system is set for convenience of the description.An x axis is set to a horizontal direction in FIG. 3, and a positiveside thereof is set to a right side in FIG. 3. A y axis is set to avertical direction in the sheet of FIG. 3, and a positive side thereofis set to an upper side. A z axis is set to a direction perpendicular tothe sheet of FIG. 3, and a positive side thereof is set to a front sideof the sheet. The driving shaft 40 (the central axis O) extends in thez-axis direction. The pump housing 2 includes a pump housing main body20 and a venturi forming block 21. The pump housing main body 20 is madefrom a metallic material. An intake port 230 and a discharge port 231are formed at the pump housing main body 20, besides each of theabove-described passages 3 and the like. The venturi forming block 21 ismade from a resin material. The venturi forming block 21 is a memberseparate from the pump housing main body 20.

The pump housing main body 20 includes a rear body 22, a side plate 23,and a front body. A containing recessed portion 220, a first hole 221, asecond hole 222, a third hole 223, a fourth hole 224, a fifth hole 225,a discharge pressure chamber 226, a valve containing hole 227, a venturiforming block containing hole 228, and a bearing holding hole are formedat the rear body 22. The containing recessed portion 220 has a bottomedcylindrical shape. The containing recessed portion 220 extends in thez-axis direction and is opened on a positive side of the rear body 22 inthe z-axis direction. Semi-cylindrical first and second groove portions(not illustrated) are formed on an inner peripheral surface of thecontaining recessed portion 220 so as to extend in the z-axis direction.The second groove portion is provided on an opposite side of a centralaxis of the containing recessed portion 220 from the first grooveportion. The bearing holding hole (not illustrated) has a bottomedcylindrical shape. The bearing holding hole extends in the z-axisdirection and is opened to a bottom portion of the containing recessedportion 220 on the negative side in the z-axis direction. A bearing ismounted on an inner periphery of the bearing holding hole. An end of thedriving shaft 40 on the negative side in the z-axis direction isinserted on an inner peripheral side of the bearing and is rotatablymounted. The discharge pressure chamber 226 is a bottomed recessedportion provided at the above-described bottom portion of the containingrecessed portion 220, and is opened to the above-described bottomportion.

The first hole 221 extends in the y-axis direction on a negative side ofthe rear body 22 in the x-axis direction and a negative side of the rearbody 22 in the z-axis direction. An opening of the first hole 22 on anegative side of the rear body 22 in the y-axis direction is sealinglyclosed by a plug member 221 a. The first hole 221 is formed so as topartially overlap the discharge pressure chamber 226 as viewed from they-axis direction and the z-axis direction, and is connected to thedischarge pressure chamber 226. The valve containing hole 227 has agenerally cylindrical shape, and extends in the x-axis direction on apositive side of the rear body 22 in the y-axis direction and a negativeside of the rear body 22 in the z-axis direction. In other words, alongitudinal direction of the valve containing hole 227 (the x-axisdirection) extends perpendicularly to a direction along the central axisO (the z-axis direction). An end of the valve containing hole 227 on thepositive side in the x-axis direction is opened on an outer surface ofthe rear body 22. This opening is sealingly closed by a plug member 227a. An end of the valve containing hole 227 on the negative side in thex-axis direction is connected to an end of the first hole 221 on thepositive side in the y-axis direction. One end of the fifth hole 225 isopened on a portion of the valve containing hole 227 that is closer tothe negative side in the x-axis direction. The other end of the fifthhole 225 is opened on the outer surface of the rear body 22.

The venturi forming block containing hole 228 has a generallycylindrical shape, and extends in the x-axis direction on the negativeside of the rear body 22 in the z-axis direction. In other words, alongitudinal direction of the venturi forming block containing hole 228(the x-axis direction) extends generally in parallel with thelongitudinal direction of the valve containing hole 227, and alsoextends perpendicularly to the direction along the central axis O (thez-axis direction). A negative side of the venturi forming blockcontaining hole 228 in the x-axis direction is formed so as to intersectthe first hole 221 and is connected to the first hole 221. Further, thenegative side of the venturi forming block containing hole 228 in thex-axis direction is formed so as to partially overlap the dischargepressure chamber 226 as viewed from the y-axis direction and the z-axisdirection, and is connected to the discharge pressure chamber 226. Anend of the venturi forming block containing hole 228 on the negativeside in the x-axis direction is opened on the outer surface of the rearbody 22. This opening is sealingly closed by a plug member 228 a. Thesecond hole 222 is provided on a generally same central axis as theventuri forming block containing hole 228, and extends in the x-axisdirection on a positive side of the rear body 22 in the x-axis directionand the negative side of the rear body 22 in the z-axis direction. Anend of the second hole 222 on the negative side in the x-axis directionis connected to an end of the venturi forming block containing hole 228on the positive side in the x-axis direction. An inner diameter of thesecond hole 222 is smaller than an inner diameter of the venturi formingblock containing hole 228. The third hole 223 extends in the z-axisdirection on the positive side of the rear body 22 in the x-axisdirection and the negative side of the rear body 22 in the z-axisdirection. An end of the third hole 223 on the positive side in thez-axis direction is connected to an end of the second hole 222 on thepositive side in the x-axis direction. An end of the third hole 223 onthe negative side in the z-axis direction is opened on the outer surfaceof the rear body 22. The fourth hole 224 connects a positive side of thevalve containing hole 227 in the x-axis direction and a positive side ofthe venturi forming block containing hole 228 in the x-axis direction toeach other.

The side plate 23 has a disk-like shape. A shaft containing hole (notillustrated) is provided at the side plate 23. The shaft containing holepenetrates through a central portion of the side plate 23. A pair ofintake ports 230 a and 230 b and a pair of discharge ports 231 a and 231b are provided on a surface of the side plate 23 on one side in an axialdirection. The pair of intake ports 230 a and 230 b is grooves extendingin a generally circular-arc manner in a direction around the shaftcontaining hole (hereinafter referred to as a circumferentialdirection), and is provided at positions opposite of the shaftcontaining hole from each other. The pair of discharge ports 231 a and231 b is grooves extending in a generally circular-arc manner in thecircumferential direction, and is provided at positions opposite of theshaft containing hole from each other. The intake ports 230 and thedischarge ports 231 are arranged alternately in the circumferentialdirection. A communication passage (not illustrated) is provided at theside plate 23. The communication passage axially penetrates though theside plate 23 to establish communication between both side surfacesthereof. A first communication passage is opened to the intake port 230.A second communication passage is opened to the discharge port 231. Theside plate 23 is installed in the containing recessed portion 220 of therear body 22. A surface of the side plate 23 on the above-described oneside faces an opening side of the containing recessed portion 220 (thepositive side in the z-axis direction). A surface of the side plate 23on the other side faces the bottom portion of the containing recessedportion 220. The shaft containing hole of the side plate 23 faces thebearing holding hole of the rear body 22. The first communicationpassage of the side plate 23 faces the bearing holding hole of the rearbody 22. The first communication passage of the side plate 23 isconnected to the intake passage 3 of the rear body 22. Each of theintake ports 230 is connected to the intake passage 3 via the firstcommunication passage. The second communication passage of the sideplate 23 is connected to the discharge pressure chamber 226 of the rearbody 22. Each of the discharge ports 231 is connected to the dischargepressure chamber 226 via the second communication passage.

A front body (not illustrated) is a pump cover. The front body is fixedto the positive side of the rear body 22 in the z-axis direction so asto sealingly close the containing recessed portion 220. A bearingholding hole is provided at the front body 24. The bearing holding holeextends in the z-axis direction. A bearing is mounted on an innerperiphery of the bearing holding hole. An end of the driving shaft 40 onthe positive side in the z-axis direction is inserted on the innerperipheral side of the bearing, and is rotatably mounted.

The venturi forming block 21 has a generally cylindrical shape. Adiameter (an outer diameter) of an outer peripheral surface of theventuri forming block 21 is approximately equal to a diameter (an innerdiameter) of an inner peripheral surface of the venturi forming blockcontaining hole 228. The venturi portion 50 is formed at the venturiforming block 21. The venturi portion 50 is a constriction portionformed at the venturi forming block 21 by molding. The venturi formingblock 21 is joined to the pump housing main body 20 after the venturiportion 50 is formed. FIGS. 3 and 4 illustrate the cross sectionacquired by cutting the venturi forming block 21 along the plane passingthrough the axis line (the central axis) along a longitudinal directionof the venturi portion 50. FIG. 5 illustrates the venturi forming block21 as viewed from a direction in which the central axis of the venturiportion 50 extends (from the negative side in the x-axis direction).Hereinafter, the direction in which the central axis of the venturiportion 50 extends will be referred to as an axial direction, and adirection around the central axis will be referred to as acircumferential direction. The venturi forming block 21 includes aninner diameter gradually-reducing portion 210, the venturi portion 50, acommunication hole 213, a first communication groove 214, and a secondcommunication groove 215. The venturi portion 50 includes a smalldiameter portion 51 and an inner diameter gradually-increasing portion52.

The inner diameter gradually-reducing portion 210 is provided so as toextend in the axial direction toward an inner peripheral side of theventuri forming block 21, and is opened on an end surface of the venturiforming block 21 on one side in the axial direction. The inner diametergradually-reducing portion 210 is a taper portion tapering from the oneside in the axial direction toward the other side in the axial direction(a downstream side in the discharge passage 5), and is formed in such amanner that an inner diameter thereof gradually reduces toward the otherside in the axial direction. An inner diameter of an end of the innerdiameter gradually-reducing portion 210 on the one side in the axialdirection is smaller than an inner diameter of the venturi forming blockcontaining hole 228. The small diameter portion 51 is provided on theinner peripheral side of the venturi forming block 21, and extends inthe axial direction. An end of the small diameter portion 51 on the oneside in the axial direction is connected to an end of the inner diametergradually-reducing portion 210 on the other side in the axial direction.An inner diameter of the small diameter portion 51 is approximatelyequal to an inner diameter of an end of the inner diametergradually-reducing portion 210 on the other side in the axial direction,and is kept constant in the axial direction.

The inner diameter gradually-increasing portion 52 is provided so as toextend in the axial direction on the inner peripheral side of theventuri forming block 21. An end of the inner diametergradually-increasing portion 52 on the one side in the axial directionis connected to an end of the small diameter portion 51 on the otherside in the axial direction, and an end of the inner diametergradually-increasing portion 52 on the other side in the axial directionis opened on an end surface of the venturi forming block 21 on the otherside in the axial direction. The inner diameter gradually-increasingportion 52 is a taper portion tapering from the other side in the axialdirection toward the one side in the axial direction (the upstream sideof the discharge passage 5), and is formed in such a manner that aninner diameter thereof gradually increases from the one side in theaxial direction toward the other side in the axial direction (thedownstream side of the discharge passage 5). An inner diameter of theend of the inner diameter gradually-increasing portion 52 on the otherside in the axial direction is slightly smaller than the inner diameterof the second hole 222. The venturi forming block 21 is formed in such amanner that a narrower angle e sandwiched between inner walls of theinner diameter-gradually increasing portion 52 (one of angles sandwichedbetween the inner walls as viewed from a direction perpendicular to thecentral axis of the venturi portion 50 that is equal to or smaller than180 degree) is 60 degrees or smaller, in particular, approximately 15degrees.

The communication hole 213 is a radial hole formed inside the venturiforming block 21 and extending in a radial direction of the venturiforming block 21. A plurality of (four) communication holes 213 areprovided, and are arranged at approximately equal intervals to oneanother in the circumferential direction. Each of the communicationholes 213 is provided at a position overlapping the small diameterportion 51 in the axial direction. A radially inner end of each of thecommunication holes 213 is opened to the small diameter portion 51. Thefirst communication groove 214 is a circumferential groove formed on anouter peripheral surface of the venturi forming block 21 and extendingin the circumferential direction. The first communication groove 214 isprovided at a position overlapping the small diameter portion 51 and thecommunication hole 213 in the axial direction. A radially outer end ofeach of the communication holes 213 is opened to the first communicationgroove 214 (a bottom portion thereof). The second communication groove215 is an axial groove formed on the outer peripheral surface of theventuri forming block 21 and extending in the axial direction. An end ofthe second communication groove 215 on the one side in the axialdirection is connected to the first communication groove 214. An end ofthe second communication groove 215 on the other side in the axialdirection is positioned close to the end surface of the venturi formingblock 21 on the other side in the axial direction.

The venturi forming block 21 is joined to the pump housing main body 20(the venturi forming block containing hole 228 of the rear body 22) asillustrated in FIGS. 3 and 4 after the venturi portion 50 is formed. Thecentral axis of the venturi forming block 21 (the venturi portion 50)extends in the x-axis direction. The above-described one side of theventuri forming block 21 in the axial direction corresponds to thenegative side in the x-axis direction, and the above-described otherside of the venturi forming block 21 in the axial direction correspondsto the positive side in the x-axis direction. The end surface of theventuri forming block 21 on the other side in the axial direction (onwhich the inner diameter gradually-increasing portion 52 is opened) isin abutment with the end surface of the venturi forming block containinghole 228 on the positive side in the x-axis direction (on which thesecond hole 222 is opened). The end of the second communication groove215 in the venturi forming block 21 on the above-described other side inthe axial direction is connected to an opening of the fourth hole 224 inthe venturi forming block containing hole 228. A third communicationgroove connected to the end of the second communication groove 215 onthe other side in the axial direction and also extending in thecircumferential direction may be provided at a position in the axialdirection that radially faces the opening of the fourth hole 224 on theouter peripheral surface of the venturi forming block 21. In this case,the end of the second communication groove 215 on the other side in theaxial direction and the opening of the fourth hole 224 are connected toeach other via the third communication groove, which eliminates anecessity of adjusting a position of the venturi forming block 21 in arotational direction around the central axis of the venturi formingblock containing hole 228.

The pump element 4 is contained in a space surrounded by the innerperiphery of the containing recessed portion 220 in the rear body 22,the surface of the side plate 23 on the positive side in the z-axisdirection, and the surface of the front body on the negative side in thez-axis direction. In other words, the above-described space functions asa pump element containing portion. The driving shaft 40 is mounted inthe above-described space, and the pump element 4 forms a plurality ofpump chambers 400 around the driving shaft 40. As illustrated in FIG. 2,the pump element 4 is a vane pump-type pump, and includes a set of arotor 41 and vanes 42. The rotor 41 is provided in the pump elementcontaining portion, and is coupled with the driving shaft 40 byserration coupling. The rotor 41 is rotationally driven by the drivingshaft 40, and rotates according to a rotation of the driving shaft 40. Aplurality of (ten) slits 410 (radially extending grooves) is eachradially provided at the rotor 41. The slits 410 are each opened on anouter peripheral surface of the rotor 41. The plurality of slits 410 areprovided at approximately equal intervals in a circumferential directionof the rotor 41. The vane 42 is set in each of the slits 410. The vane42 is a generally rectangular plate member (a vane). The vane 42 isprovided so as to be able to project from the slit 410 and retract intothe slit 410 (provided in a projectable and retractable manner).

A cam ring 43 has an annular shape. An outer periphery of the cam ring43 is fitted in the inner periphery of the containing recessed portion220. A center (a central axis) of the cam ring 43 approximatelycoincides with the central axis O. An inner peripheral surface of thecam ring 43 has a cylindrical shape extending in the z-axis direction,and is generally ecliptic as viewed from the z-axis direction.Semi-cylindrical first and second groove portions 431 and 432 areprovided on an outer peripheral surface of the cam ring 43. The secondgroove portion 432 is provided on an opposite side of the central axis Oof the cam ring 43 from the first groove portion 431. A first pin 451 ismounted by being fitted between the above-described first groove portionof the containing recessed portion 220 and the first groove portion 431of the cam ring 43. A second pin 452 is mounted by being fitted betweenthe above-described second groove portion of the containing recessedportion 220 and the second groove portion 432 of the cam ring 43. Eachof the pins 451 and 452 is fixed to the pump housing main body 20. Thepints 451 and 452 prevent or reduce a rotation of the cam ring 43relative to the pump housing 2. The cam ring 43 is disposed around therotor 41 in the pump element containing portion. The cam ring 43 formsthe plurality of pump chambers 400 together with the rotor 41 and thevanes 42. In other words, the side plate 23 and the front body 24 aredisposed on side surfaces of the cam ring 43 and the rotor 41 in theaxial direction. A space between an inner peripheral surface of the camring 43 and an outer peripheral surface of the rotor 41 is sealinglyclosed by the side plate 23 and the front body 24 on the both sidesthereof in the axial direction, while being divided into the pluralityof (ten) pump chambers (volume chambers) 400 by the plurality of vanes42.

For convenience of the description, an X axis and a Y axis are set to along-axis direction and a short-axis direction of the generally eclipticinner peripheral surface of the cam ring 43, respectively, asillustrated in FIG. 2. The rotor 41 rotates in a counterclockwisedirection in FIG. 2. A radial distance between the outer peripheralsurface of the rotor 41 and the inner peripheral surface of the cam ring43 (a radial dimension of the pump chamber 400) increases as approachingthe negative side in the X-axis direction from the central axis O of thecam ring 43, or approaching the positive side in the X-axis directionfrom the central axis O. The vane 42 projects from the slit 410according to this change in the distance, by which each of the pumpchambers 400 is defined. A volume of the pump chamber 400 increases asapproaching the negative side in the X-axis direction from the centralaxis O or approaching the positive side in the X-axis direction from thecentral axis O. Due to this difference in the volume of the pump chamber400, the volume of the pump chamber 400 reduces on the positive side inthe X-axis direction with respect to the central axis O while increasingon the negative side in the X-axis direction with respect to the centralaxis O, as the rotor 41 rotates (as the pump chamber 400 travels towardthe negative side in the x-axis direction) on the positive side in theY-axis direction with respect to the central axis O. The volume of thepump chamber 400 reduces on the negative side in the X-axis directionwith respect to the central axis O while increasing on the positive sidein the X-axis direction with respect to the central axis O, as the rotor41 rotates (the pump chamber 400 travel toward the positive side in theX-axis direction) on the negative side in the Y-axis direction withrespect to the central axis O.

In this manner, the pump chamber 400 periodically expands and contractswhile rotating in the counterclockwise direction around the central axisO. The intake port 230 is opened to a region on the negative side in theX-axis direction and the positive side in the Y-axis direction, and aregion on the positive side in the X-axis direction and the negativeside in the Y-axis direction. In other words, the intake port 230 isopened to an intake region where the volume of the pump chamber 400increases according to the rotation of the driving shaft 40 (i.e., anintake region where the pump chamber 400 increasing in volume accordingto the rotation of the driving shaft 40 among the plurality of pumpchambers 400 is located). The discharge port 231 is opened to a regionon the positive side in the X-axis direction and the positive side inthe Y-axis direction, and a region on the negative side in the X-axisdirection and the negative side in the Y-axis direction. In other words,the discharge port 231 is opened to a discharge region where the volumeof the pump chamber 400 reduces according to the rotation of the drivingshaft 40 (i.e., a discharge region where the pump chamber 400 reducingin volume according to the rotation of the driving shaft 40 among theplurality of pump chambers 400 is located). The pump chamber 400introduces the hydraulic fluid therein from the intake port 230 in theintake region, and discharges the (above-described introduced) hydraulicfluid into the discharge port 231 in the discharge region. The intakeand the discharge are each carried out twice per rotation of the drivingshaft 40 in correspondence with the pair of intake ports 230 a and 230 band the pair of discharge ports 231 a and 231 b. The hydraulic fluid inboth the discharge ports 231 are collected into one portion. The camring 43 is provided immovably in the pump element containing portion. Inother words, the pump element 4 is a fixed displacement pump thatdischarges a constant amount as a discharge amount per rotation of thedriving shaft 40 (hereinafter referred to as a pump capacity). The pumpelement 4 may be a set of trochoidal pump-type inner and outer rotors ormay be another type of pump.

The control valve 8 is a spool valve body and is contained in the valvecontaining hole 227. The control valve 8 is displaceable (capable ofperforming a stroke) in the x-axis direction in the valve containinghole 227. The control valve 8 includes a first land portion 81, a secondland portion 82, a connection portion 83, a spacer portion 84, and arecessed portion 85. Each of the land portions 81 and 82 is cylindrical,and diameters thereof are approximately equal to each other. A diameterof an outer peripheral surface of each of the land portions 81 and 82 isslightly smaller than a diameter of an inner peripheral surface of thevalve containing hole 227. In the control valve 8, the first landportion 81 is provided on the negative side in the x-axis direction andthe second land portion 82 is provided at an end on the positive side inthe x-axis direction. A circumferential groove 810 extending in adirection around the central axis of the control valve 8 (hereinafterreferred to as a circumferential direction) is provided on an outerperipheral surface of the first land portion 81. A plurality ofcircumferential grooves 820 extending in the circumferential directionis provided on an outer peripheral surface of the second land portion82. The connection portion 83 has a cylindrical shape sandwiched betweenboth the land portions 81 and 82 and extending in the x-axis direction.A diameter of the outer peripheral surface of the connection portion 83is smaller than each of the land portions 81 and 82. The spacer portion84 has a rod shape extending from the first land portion 81 toward thenegative side in the x-axis direction. The recessed portion 85 has abottomed cylindrical shape and extends in the x-axis direction insidethe second land portion 82. The recessed portion 85 is opened on an endsurface of the second land portion 82 on the positive side in the x-axisdirection.

A high pressure chamber 86 is defined inside the valve containing hole227 by being surrounded by an end surface of the first land portion 81on the negative side in the x-axis direction and the inner peripheralsurface of the valve containing hole 227. An intermediate pressurechamber 88 is defined by being surrounded by an end surface of thesecond land portion 82 on the positive side in the x-axis direction, theinner peripheral surface of the valve containing hole 227, and an endsurface of the plug member 227 a on the negative side in the x-axisdirection. A drain chamber 89 is defined on an outer periphery of theconnection portion 83 between the first land portion 81 and the secondland portion 82. A spring 88 is mounted in the intermediate pressurechamber 88. The spring 88 is a coil spring. An end of the spring 88 onthe positive side in the x-axis direction is held by the plug member 227a. A negative side of the spring 88 in the x-axis direction is heldinside the recessed portion 85 of the control valve 8. The spring 88 ismounted in a compressed state. The spring 88 is a return springconstantly biasing the control valve 8 toward the negative side in thex-axis direction. A displacement of the control valve 8 in the valvecontaining hole 227 toward the negative side in the x-axis direction isregulated by abutment of an end of the spacer portion 84 on the negativeside in the x-axis direction with an end surface of the valve containinghole 227 on the negative side in the x-axis direction. The first hole221 is opened to the high pressure chamber 86 and the fourth hole 224 isopened to the intermediate pressure chamber 88, regardless of thedisplacement of the control valve 8 in the valve containing hole 227.

Next, a configuration of the plurality of passages 3 and the like willbe described. Each of the discharge ports 231 of the side plate 23 is incommunication with the first hole 221 or the venturi forming blockcontaining hole 228 via the discharge pressure chamber 226 of the rearbody 22. A portion where the discharge pressure chamber 226 and thefirst hole 221 or the venturi forming block containing hole 228 areconnected to each other, a negative side of the venturi forming blockcontaining hole 228 in the x-axis direction with respect to the venturiforming block 21 (the inner diameter gradually-reducing portion 210),and the inner diameter gradually-reducing portion 210 function as thedischarge passage 5 from the discharge port 231 (the discharge pressurechamber 226) to the venturi portion 50 (the small diameter portion 51and the inner diameter gradually-increasing portion 52), i.e., thedischarge passage 5 on the upstream side of the venturi portion 50. Thesmall diameter portion 51 is formed in such a manner that the innerdiameter thereof is smaller than an inner diameter of theabove-described discharge passage 5. The inner diametergradually-increasing portion 52 of the venturi portion 50 is incommunication with outside the rear body 22 via the second hole 222 andthe third hole 223. The second hole 222 and the third hole 223 functionas the discharge passage 5 extending from the venturi portion 50 towardthe CVT 10, i.e., the discharge passage 5 on the downstream side of theventuri portion 50. An inner diameter of the above-described dischargepassage 5 is larger than an inner diameter of an end of the innerdiameter gradually-increasing portion 52 on the positive side in thex-axis direction. A portion between portions of the first hole 221 thatare connected to (intersects) the venturi forming block containing hole228 and the valve containing hole 227, respectively, functions as thehigh pressure passage 6 branching off from the discharge passage 5 onthe upstream side of the venturi portion 50 and is connected to the highpressure chamber 86 of the control valve 8. The communication hole 213,the first communication groove 214, and the second communication groove215 of the venturi forming block 21, and the fourth hole 224 of the rearbody 22 function as the intermediate pressure passage 7 (a venturiportion pressure introduction passage) branching off from the venturiportion 50 (the small diameter portion 51) in the discharge passage 5and is connected to the intermediate pressure chamber 88 of the controlvalve 8. The communication hole 213 functions as a venturi portionpressure introduction hole. The fifth hole 225 of the rear body 22functions as the return passage 9 extending from the drain chamber 89 ofthe control valve 8 toward the oil pan 100.

As illustrated in FIGS. 3 and 4, the longitudinal direction of theventuri portion 50 (the x-axis direction) extends generallyperpendicularly to the direction in which the central axis O of thedriving shaft 40 extends (the z-axis direction), and also extendsgenerally in parallel with the longitudinal direction of the controlvalve 8 (the x-axis direction). The venturi portion 50 is disposed insuch a manner that the upstream side thereof faces the high pressurechamber 86 of the control valve 8. In other words, the discharge passage5 on the upstream side of the venturi portion 50 and the high pressurechamber 86 at least partially overlap each other in the x-axisdirection. More specifically, the negative side of the venturi formingblock containing hole 228 in the x-axis direction with respect to theventuri forming block 21, and the high pressure chamber 86 (when thecontrol valve 8 is maximally displaced toward the negative side in thex-axis direction) at least partially overlap each other as viewed fromthe y-axis direction.

[Functions]

Next, functions and effects will be described. An upper diagram of FIG.6 schematically illustrates the discharge passage 5 around the venturiportion 50. An arrow indicates the direction in which the hydraulicfluid flows. It is defined that u₁ and p₁ represent a flow speed and apressure of the hydraulic fluid in the discharge passage 5 on theupstream side of the venturi portion 50, respectively. It is definedthat u₂ and p₂ represent a flow speed and a pressure at the smalldiameter portion 51. It is defined that u₃ and p₃ represent a flow speedand a pressure in the discharge passage 5 on the downstream side of theventuri portion 50, respectively. A lower diagram of FIG. 6 illustratesa change in the pressure P that is associated with each of the portionsillustrated in the upper diagram. The inner diameter (a cross-sectionalarea) of the small diameter portion 51 is smaller than the innerdiameter (a cross-sectional area) of the discharge passage 5 on theupstream side of the venturi portion 50. Therefore, u₂ is higher thanu₁. This increase in the flow speed is proportional to the flow amountand inversely proportional to a difference in the cross-sectional area.The pressure reduces in a quadratic function manner according to theincrease in the flow speed based on Bernoulli's principle. Therefore, p₂is lower than p₁. This reduction in the pressure corresponds to theincrease in the flow speed, i.e., the flow amount. In this manner, adifferential pressure Δp=p₁−p₂ is generated according to the flow amountat the venturi portion 50 (the small diameter portion 51) as theconstriction portion. The inner diameter of the inner diametergradually-increasing portion 52 gradually increases at the venturiportion 50 as approaching the downstream side. Therefore, the flow speedat the inner diameter gradually-increasing portion 52 gradually reducesas approaching the downstream side. Since the reduction in the flowspeed is gentle, energy is not lost so much. Therefore, the pressure inthe inner diameter gradually-increasing portion 52 gradually increasesas the hydraulic fluid flows toward the downstream side, according tothe reduction in the flow speed. If the inner diameter on the downstreamside at the venturi portion 50 increases to around the inner diameter ofthe discharge passage 5 on the upstream side of the venturi portion 50,the flow speed reduces to around u₁, and the pressure increases(recovers) to around p₁. Since the inner diameter of the constrictionportion on the downstream side (the inner diameter gradually-increasingportion 52) gently increases in this manner, a large loss of energy isprevented or cut down. Therefore, on the downstream side of theconstriction portion, the flow speed reduces to a similar level to theupstream side of the constriction portion, and the pressure alsorecovers to a similar level to the upstream side of the constrictionportion.

The hydraulic fluid (p₁) on the upstream side of the venturi portion 50is introduced into the high pressure chamber 86 via the high pressurepassage 6. The hydraulic fluid (p₂) in the venturi portion 50 (the smalldiameter portion 51) is introduced into the intermediate pressurechamber 88 via the intermediate pressure passage 7. The drain chamber 89is kept at the low pressure (is opened to an atmospheric pressuresimilarly to the intake passage 3). A force F1 toward the positive sidein the x-axis direction due to pi in the high pressure chamber 86 and aforce F2 toward the negative side in the x-axis direction due to p₂ inthe intermediate pressure chamber 88 are applied to the control valve 8.Further, a force F3 toward the negative side in the x-axis direction dueto the spring 88 is applied to the control valve 8. When the differencebetween F1 and F2, F1−F2 (the force corresponding to the differentialpressure Δp) exceeds F3, the control valve 8 is displaced toward thepositive side in the x-axis direction. When the high pressure chamber 86and the return passage 9 are brought into communication with each otherdue to this displacement, the hydraulic fluid introduced from thedischarge passage 5 on the upstream side of the venturi portion 50 tothe high pressure passage 6 (the high pressure chamber 86) starts to bereturned to the intake passage 3 (one side where the intake ports 230are located) via the return passage 9. In other words, the control valve8 switches the flow passage in such a manner that the hydraulic fluid isreturned toward the intake side based on the differential pressure Δpbetween the upstream side of the venturi portion 50 and the smalldiameter portion 51. When the hydraulic fluid starts to be returnedtoward the intake side, the flow amount to be supplied to the CVT 10 viathe discharge passage 5 is limited to a required amount. In this manner,the venturi portion 50, the high pressure passage 6, the intermediatepressure chamber 7, the control valve 8, and the return passage 9function as a controller that controls the discharge flow amount of thepump element 4.

In the conventional pump apparatus, the orifice has been used as a meansfor generating the differential pressure. The orifice can be formedwith, for example, such a simple structure that only a constriction of athin plate is provided in the flow passage. The pressure difference isgenerated according to the flow amount between the upstream side and thedownstream side of the orifice. However, the orifice leads to aturbulence of the flow at an exit of the constriction, thereby resultingin a loss of the energy and thus a reduction in the pressure on thedownstream side of the orifice. The lost energy undesirably spreadsoutward by being converted into heat, noise, and the like. Therefore,the efficiency of the pump undesirably reduces. As the differentialpressure is further increasing, the efficiency of the pump is reducing.Hereinafter, a pump apparatus similar to the present exemplaryembodiment that uses an orifice 500 instead of the venturi portion 50will be referred to as a comparative example. A narrower angle θ at anexit of the orifice 500 is 120 to 180 degrees. FIG. 7 is a similardiagram to FIG. 6 that illustrates the comparative example. An upperdiagram of FIG. 7 illustrates the discharge passage 5 around the orifice500. It is defined that u₁ and p₁ represent the flow speed and thepressure of the hydraulic fluid in the discharge passage 5 on theupstream side of the orifice 500, respectively. It is defined that u₂and p₂ represent the flow speed and the pressure in the dischargepassage 5 on the downstream side of the orifice 500, respectively. Aninner diameter of the orifice 500 is smaller than the inner diameter ofthe discharge passage 5 on the upstream side of the orifice 500.Therefore, the flow speed at the orifice 500 is higher than and thepressure at the orifice 500 is lower than p₁. An inner diameter of theexit of the orifice 500 suddenly increases as approaching the downstreamside. Therefore, an eddy current occurs at the exit of the orifice 500,and the energy is significantly lost. Therefore, although u₂ reduces tou₁, p₂ does not increase (recover) to p₁. In other words, the pressureundesirably reduces (a pressure loss). The conventional pump apparatusresults in supply of the pressure p₂ to the CTV 10 after the pressurereduces in this manner.

On the other hand, the pump apparatus 1 according to the presentembodiment uses a venturi tube instead of the orifice as method meansfor generating the differential pressure. The venturi portion 50 has thegently increasing inner diameter on the downstream side (the innerdiameter gradually-increasing portion 52) of the constriction portion,thereby preventing or cutting down the significant loss of the energy.Therefore, the pressure recovers according to the reduction in the flowspeed. In other words, the pressure loss at a differential pressuregeneration means is prevented or cut down. Therefore, the presentembodiment can generate the differential pressure while preventing orreducing the deterioration of the efficiency of the pump. Especially,the automatic transmission such as the stepless transmission uses alarger flow amount compared to a power steering apparatus and the like,and therefore can acquire a considerable effect of preventing or cuttingdown the pressure loss. An entrance at the constriction portion at theventuri portion 50 (the upstream side of the small diameter portion 51)is also formed in such a manner that the dimeter of the inner diametergradually-reducing portion 210 gently reduces, which can prevent orreduce the occurrence of the turbulence of the flow. As a result, theenergy is not lost significantly, and the pressure reduces according tothe increase in the flow speed. Therefore, the present embodiment canfurther efficiently reduce the pressure (can prevent or cut down thepressure loss as a whole). Therefore, the present embodiment can furtherimprove the efficiency of the pump.

In the comparative example, an attempt to cut down the energy loss atthe orifice 500 to prevent or reduce the deterioration of the efficiencyof the pump leads to an unintentional reduction in the differentialpressure (the force F1−F2 corresponding thereto). Activating the controlvalve 8 with the small Δp leads to an unstable behavior of the controlvalve 8. As a result, a wide variation undesirably occurs in thedischarge flow amount of the pump element 4 targeted for the control(hereinafter referred to as a control flow amount). On the other hand,the present embodiment can increase the differential pressure (the forceF1−F2 corresponding thereto) while preventing or reducing thedeterioration of the efficiency of the pump. Therefore, the presentembodiment can also prevent or reduce the above-described variation inthe control flow amount. FIG. 8 is a graph indicating a relationshipbetween the discharge flow amount (the flow amount passing through thedifferential pressure generation means) Q of the pump element 4, and thedifference Δp between the pressures applied to the both sides of thecontrol valve 8 in the axial direction (the differential pressuregenerated at the differential pressure generation means). Supposing thatthe efficiency of the pump (the pressure loss at the differentialpressure generation means) is the same between the present embodimentand the comparative example, a characteristic of the present embodimentis indicated by a solid line, and a characteristic of the comparativeexample is indicated by an alternate long and short dash line. Accordingto Q, Δp changes in a quadratic curve manner. The activation(displacement) of the control valve 84 is controlled according to Δp,i.e., Q. A change rate of Δp to Q is higher in the present embodimentthan in the comparative example. Q required to generate the same levelof Δp is smaller in the present embodiment than in the comparativeexample. In other words, a larger pressure of Δp (the force F1−F2corresponding thereto) can be generated in the present embodiment thanin the comparative example even if Q is the same therebetween.Therefore, the present embodiment can stabilize the behavior of thecontrol valve 8, and prevent or reduce the variation in the control flowamount.

Further, a load from outside (an external force) may be applied to thecontrol valve 8 besides F1 to F3. In this case, the control flow amountmay deviate from an originally intended amount. For example, there is arelatively large amount of contamination in the hydraulic fluid under ause environment in the automatic transmission (the CVT 10). If a load isgenerated on the control valve 8 due to, for example, the presence ofthe contamination in a gap between the outer peripheral surface of thecontrol valve 8 and the inner peripheral surface of the valve containinghole 227, this makes the control valve 8 less movable, therebyundesirably causing the deviation of the control flow amount from theoriginally intended amount by a flow amount corresponding to this load.On the other hand, in the present embodiment, the differential pressureΔp (the force F1−F2 corresponding thereto) can be considerably changedwith a small change in the flow amount Q. Therefore, the deviation ofthe control amount can be reduced. In FIG. 8, it is defined that δprepresents the above-described load converted into Δp, and δQ representsthe deviation of Q corresponding to this δp. In other words, apredetermined amount of Q corresponds to an arbitrary pressure of Δp,and a deviation of the above-described arbitrary pressure of Δp by δpcauses a deviation of Q from the above-described predetermined amount ofQ by δQ. The change rate of Q to Δp is smaller in the present embodimentthan in the comparative example. Therefore, δQ corresponding to the samedeviation of δp is smaller in the present embodiment than in thecomparative example (δQ₂<δQ₁). In other words, even when the same loadis applied to the control valve 8, the flow amount is less changed inthe present embodiment than in the comparative example. Therefore, thepresent embodiment can reduce the deviation of the control flow amount.

Then, it is also conceivable to increase a gap area of a clearanceportion between the control valve 8 and the valve containing hole 227around the control valve 8 to prevent a lock of the control valve 8 dueto the contamination. However, the increase in the gap area of theclearance portion leads to an increase in a leak amount around thecontrol valve 8 (via the clearance portion). This results in theundesirable deterioration of the efficiency of the pump. On the otherhand, the present embodiment can generate a large differential pressureΔp with a relatively small flow amount Q while preventing or cuttingdown the energy loss at the constriction portion. Therefore, thediameter of the control valve 8 can be reduced without requiring asignificant reduction in the force F1−F2 applied to the control valve 8.Reducing the diameter of the control valve 8 also allows a reduction inthe gap area of the above-described clearance portion. As a result, thepresent embodiment reduces the leak amount around the control valve 8,thereby succeeding in preventing or reducing the deterioration of thepump efficiency.

The narrower angle e sandwiched between the inner walls of the innerdiameter gradually-increasing portion 52 is an angle by which the exitflares at the venturi portion 50 as the constriction portion. Setting θto 60 degrees or smaller can acquire a sufficient effect of preventingor cutting down the pressure loss. FIG. 9 illustrates a relationshipbetween θ and a pressure loss rate. The pressure loss rate is a ratewhen the pressure rate in the comparative example is defined to be 1.When θ is 60 degrees or smaller, the pressure loss rate falls below 1.In other words, the pressure loss is smaller than the comparativeexample. In the present embodiment, the venturi portion 50 (the innerdiameter gradually-increasing portion 52) is formed in such a mannerthat θ becomes 60 degrees or smaller. Therefore, the pressure loss isprevented or cut down more than in the comparative example. Therefore,the present embodiment can further reliably prevent or reduce thedeterioration of the pump efficiency. For example, by setting θ toapproximately 15 degrees, the present embodiment can prevent or cut downan excessive increase in the length of the venturi portion 50 in thelongitudinal direction (a dimension in the axial direction) whileacquiring a sufficiency effect of preventing or cutting down thepressure loss.

The space in the venturi forming block containing hole 228 on thenegative side in the x-axis direction with respect to the venturiforming block 21 functions as the discharge passage 5 on the upstreamside of the venturi portion 50. The second hole 222 functions as thedischarge passage 5 on the downstream side of the venturi portion 50.The inner diameter of the venturi forming block containing hole 228 islarger than the inner diameter of the second hole 222. In other words,the above-described space in the discharge passage 5 on the upstreamside of the venturi portion 50 is a large diameter portion 53 having alarger inner diameter than the downstream side (the second hole 222).The pressure in this large diameter portion 53 is introduced into thehigh pressure chamber 86 of the control valve 8 as the pressure on theupstream side of the venturi portion 50 (the high pressure). Therefore,FIG. 6 can be redrawn like FIG. 10. In FIG. 10, it is defined that u₁*and p₁* represent a flow speed and a pressure in the large diameterportion 53. The other symbols are similar to FIG. 6. If the innerdiameter (the cross-sectional area) of the large diameter portion 53 islarger than the inner diameter (the cross-sectional area) of thedischarge passage 5 on the upstream side of the large diameter portion53, u₁* is lower than u₁ (≈u₃). According thereto, p₁* is higher than p₁(≈p₃). The other characteristics are similar to FIG. 6. Therefore,defining that Δp* represents the differential pressure generated at theventuri portion 50 (the small diameter portion 51),Δp*(=p₁*−p₂)>Δp(=p₁−p₂) is satisfied, so that a larger differentialpressure is generated than when the large diameter portion 53 is notprovided (FIG. 6). As a result, the difference F1−F2 between the forcesapplied to the control valve 8 increases, so that the present embodimentcan further effectively acquire the above-described functions andeffects.

The inner diameter of the end of the inner diameter gradually-increasingportion 52 on the other end in the axial direction that is opened on theend surface of the venturi forming block 21 on the other side in theaxial direction is slightly smaller than the inner diameter of thesecond hole 222. Therefore, FIG. 6 can be redrawn like FIG. 11. Theinner diameter gradually-increasing portion 52 includes the taperportion on the upstream side that is formed so as to keep θ constant at60 degrees or smaller (in particular, approximately 15 degrees), and astepped portion on the downstream side that is formed so as to have θlarger than 60 degrees continuously from the discharge passage 5 on thedownstream side of the venturi portion 50. Hereinafter, theabove-described taper portion on the upstream side will be referred toas a front portion 520, and the above-described stepped portion on thedownstream side will be referred to as a rear portion 521. The innerdiameter gradually-increasing portion 52 includes the front portion 520and the rear portion 521. In the present embodiment, θ of the rearportion 521 is approximately 180 degrees. In other words, the rearportion 521 flares as if extending generally perpendicularly to theinner walls of the discharge passage 5 on the downstream side of theventuri portion 50. Hypothetically supposing that the inner diametergradually-increasing portion 52 is formed as far as the inner diameterthereof reaches the same diameter as the inner diameter of the dischargepassage 5 on the downstream side of the venturi portion 50 with θ keptconstant at 60 degrees or smaller, L0 is defined to represent a lengthof this (hypothetical) inner diameter gradually-increasing portion 52 inthe longitudinal direction at this time. Then, L is defined to representa length of the front portion 520 in the longitudinal direction.

FIG. 12 illustrates a relationship between L/L0, which is a ratio of Lto L0, and the pressure loss rate. The pressure loss rate is a rate of apressure loss when L/L0 is 0, i.e., a rate when the pressure loss in thecomparative example is defined to 1. In a range where L/L0 is higherthan 0 and equal to or lower than 0.65, the pressure loss rate reducesaccording to the increase in L/L0. In a range where L/L0 is higher than0.65, the pressure loss rate does not reduce more than that even whenL/L0 increases. Therefore, as long as a region of a certain length isensured as the region where θ is 60 degrees or smaller (the frontportion 520), the pressure loss can be more prevented or cut down thanin the comparative example. However, even if the length L of the frontportion 520 increases to longer than 65% of L0, this does not achievethe effect of preventing or cutting down the pressure loss more thanthat. Therefore, it is preferable to form the front portion 520 in sucha manner that the L/L0 exceeds 0 and reaches or falls below 0.65, i.e.,as far as a position where L reaches or falls below 65% of L0. In thiscase, the rear portion 521 where θ exceeds 60 degrees is provided on thedownstream side of the front portion 520. Stopping keeping θ at 60degrees or smaller at the rear portion 521 in this manner allows theventuri portion 50 to be formed continuously from the discharge passage5 (the inner diameter of the venturi portion 50 to be returned to theinitial diameter) on the downstream side, with a relatively short length(shorter than L0). As a result, the present embodiment can reduce thelength of the venturi portion 50 in the longitudinal direction. Thepresent embodiment can improve the above-described effect of reducingthe length by allowing θ at the rear portion 521 to approach generally180 degrees as illustrated in FIG. 11. In the range where L/L0 is higherthan 0 and equal to or lower than 0.65, a reduction amount (a reductionrate) of the pressure loss rate with respect to the increase in L/L0increases as L/L0 approaches 0. Then, in a range where L/L0 is 0.4 orhigher, a sufficiently low pressure loss rate (sufficiently close to thepressure loss rate when L/L0 is 0.65) can be acquired. Therefore, it ispreferable to form the front portion 520 in such a manner that L/L0reaches or exceeds 0.4, i.e., as far as a position where L reaches orexceeds 40% of L0. In this case, the present embodiment can improve theabove-described effect of reducing the length by allowing L to approach40% of L0 while acquiring the sufficient effect of preventing or cuttingdown the pressure loss.

The venturi portion 50 is long compared to the orifice (the dimension inthe axial direction is large). Therefore, processing thereof iscomparatively difficult. On the other hand, in the present embodiment,the venturi portion 50 is formed in the venturi forming block 21. Thisventuri forming block 21 is joined to the pump housing main body 20.

As a result, the venturi portion 50 is realized inside the pump housingmain body 20. In this manner, the present embodiment can improveworkability of the venturi portion 50 by forming the venturi portion 50in the venturi forming block 21 that is a separate member from the pumphousing main body 20. The present embodiment can be realized by formingat least the small diameter portion 51 and the inner diametergradually-increasing portion 52 constituting the venturi portion 50 inthe venturi forming block 21. In other words, the constriction portionhaving the same diameter as the small diameter portion 51 and apredetermined length and the inner diameter gradually-reducing portion210 may be provided on the pump housing main body 20 side, or may beprovided on the venturi forming block 21 side. The venturi forming block21 is made from the resin material. The venturi portion 50 including theinner diameter gradually-increasing portion 52 is formed by molding.Therefore, the inner diameter gradually-increasing portion 52 can beeasily formed compared to forming the inner diametergradually-increasing portion 52 by machining processing.

Further, the venturi portion 50 should have a long dimension (a largespace in the longitudinal direction) compared to the orifice. On theother hand, in the present embodiment, the venturi portion 50 isdisposed in such a manner that the longitudinal direction of the venturiportion 50 (the x-axis direction) and the direction of the rotationalaxis (the central axis O) of the driving shaft 40 (the z-axis direction)extend generally perpendicularly to each other.

Therefore, the present embodiment can prevent or cut down an increase inthe dimension of the pump apparatus in the direction of the rotationalaxis of the driving shaft 40 (the axial direction). On the other hand,the pump housing 2 has a dimension enough to contain the control valve 8therein from the beginning. Then, in the present embodiment, the venturiportion 50 is disposed in such a manner that the longitudinal directionof the venturi portion 50 and the longitudinal direction of the controlvalve 8 extend generally in parallel with each other. The venturiportion 50 is disposed so as to utilize the originally existing spaceextending in the longitudinal direction of the control valve 8 in thismanner, so that the present embodiment can prevent or cut down theincrease in a size of an outer shape of the pump apparatus (in theradial direction of the control valve 8).

Further, the venturi portion 50 is disposed in such a manner that thedischarge passage 5 on the upstream side of the venturi portion 50 facesthe high pressure chamber 86 of the control valve 8. Therefore, thepresent embodiment can shorten the high pressure passage 6 (the firsthole 221) establishing the communication between the upstream side ofthe venturi portion 50 and the high pressure chamber 86. Morespecifically, both the venturi forming block containing hole 228 and thevalve containing hole 227 extend in the x-axis direction and aredisposed generally in parallel with each other. The first hole 221extends linearly in the y-axis direction, and connects the negative sideof the venturi forming block containing hole 228 in the x-axis directionwith respect to the venturi forming block 21 and the high pressurechamber 86 in the valve containing hole 227 to each other, therebyconnecting the upstream side of the venturi portion 50 and the highpressure chamber 86 with a shortest distance. The venturi portion 50 maybe disposed in such a manner that the second communication groove 215(at least a part thereof) in the venturi forming block 21 faces theintermediate pressure chamber 88 of the control valve 8. In this case,the present embodiment can shorten the intermediate pressure passage 7(the fourth hole 224) establishing the communication between the secondcommunication groove 215 and the intermediate pressure chamber 88.

The communication holes 213 of the venturi forming block 21 are openedon the inner peripheral surface of the venturi portion 50 on theradially inner side. The communication holes 213 are provided in theventuri portion 50, and function as openings for introducing thepressure in the venturi portion 50 into the control valve 8 (theintermediate pressure chamber 88). Then, due to presence of, forexample, a bend or a curve in the discharge passage 5 on the upstreamside of the venturi portion 50, this passage 5 may have unevenness in aflow speed distribution in a direction around the axis line along thelongitudinal direction thereof(hereinafter referred to as acircumferential direction). This case also leads to occurrence ofunevenness in a pressure distribution in the circumferential directionin the venturi portion 50. This unevenness undesirably varies dependingon the flow amount and a temperature condition. On the other hand, inthe present embodiment, the plurality of (four) openings is provided inthe circumferential direction of the venturi portion 50 as theabove-described openings of the communication holes 213. The pressure isextracted from a plurality of portions in the circumferential directionin the venturi portion 50 in this manner, which allows the pressure inthe venturi portion 50 to be stably introduced into the intermediatepressure chamber 88 in spite of the above-described unevenness in thepressure distribution. In other words, the pressures (the hydraulicfluid) extracted from the above-described openings of the plurality ofcommunication holes 213 are collected into the single intermediatepressure passage 7 (the fourth hole 224) via the first and secondcommunication grooves 214 and 215, and then are introduced into theintermediate pressure chamber 88. At this time, the above-describeduneven pressure distributions are canceled out by each other, whichresults in introduction of an average pressure in the circumferentialdirection in the venturi portion 50 into the intermediate pressurechamber 88. Therefore, the variation in the pressure extracted frominside the venturi portion 50 is reduced. Therefore, the activation ofthe control valve 8 is stabilized, and the deviation of the control flowamount is reduced. The number of communication holes 213 may be anynumber as long as this number is two or more. In the present embodiment,the above-described openings of the communication holes 213 are disposedat generally equal intervals in the circumferential direction, so thatthe present embodiment can further stably reduce the variation in thepressure extracted from inside the venturi portion 50.

The communication holes 213 are provided at the positions overlappingthe small diameter portion 51 in the axial direction (the longitudinaldirection) of the venturi portion 50. In other words, theabove-described openings of the communication holes 213 are provided atthe small diameter portion 51. Therefore, this configuration results inextraction of the pressure from a portion smallest in diameter in theventuri portion 50, i.e., a portion in the venturi portion 50 where thepressure is minimized, and introduction of this pressure into theintermediate pressure chamber 88. As a result, the present embodimentcan most efficiently utilize the differential pressure generated in theventuri portion 50.

Second Embodiment

The pump apparatus 1 according to a second embodiment is different fromthe first embodiment in terms of the configuration of the venturiforming block 21. The second embodiment will be described below focusingon only configurations different from the first embodiment.Configurations shared with the first embodiment will be identified bythe same reference numerals as the first embodiment, and descriptionsthereof will be omitted. FIG. 13 illustrates a cross section acquired bycutting the venturi forming block 21 along a plane passing through thecentral axis of the venturi portion 50. The venturi forming block 21 isnot provided with the inner diameter gradually-reducing portion 210 likethe first embodiment. The small diameter portion 51 is opened on the endsurface of the venturi forming block 21 on the one side in the axialdirection (the outer surface of the venturi forming block 21). Thecommunication hole 213 is provided at the position overlapping the oneside of the inner diameter gradually-increasing portion 52 in the axialdirection (the one side where the small diameter portion 51 is located).A radially inner end of the communication hole 213 is opened to the oneside of the inner diameter gradually-increasing portion 52 in the axialdirection (the one side where the small diameter portion 51 is located).The communication hole 213 forms a part of the intermediate pressurepassage 7. The communication hole 213 introduces a pressure on the oneside of the inner diameter gradually-increasing portion 52 in the axialdirection (the one side where the small diameter portion 51 is located)among pressures in the venturi portion 50 into the intermediate pressurechamber 88 of the control valve 8.

Next, functions will be described. Like the present embodiment, thepressure in the venturi portion 50 that is introduced into theintermediate pressure chamber 88 may be not only the pressure in thesmall diameter portion 51 but also the pressure in the inner diametergradually-increasing portion 52. The pressure on the one side of theinner diameter gradually-increasing portion 52 in the axial direction(the one side where the small diameter portion 51 is located) isintroduced into the intermediate pressure chamber 88. Therefore, a lowerpressure among the pressures in the inner diameter gradually-increasingportion 52 can be used. Therefore, the present embodiment allows asufficiently large differential pressure to be applied to the controlvalve 8.

If the small diameter portion 51 is not opened on the outer surface ofthe venturi forming block 21 and is provided inside the venturi formingblock 21, a mold would have to be inserted from the both sides of theventuri forming block 21 in the axial direction when the venturi portion50 is formed by molding. When the venturi portion 50 is subjected to themachining processing, the machining processing would have to beperformed from the both sides of the venturi forming block 21 in theaxial direction. On the other hand, in the present embodiment, the smalldiameter portion 51 is opened on the outer surface of the venturiforming block 21. Therefore, when the venturi portion 50 is formed bymolding, this can be achieved by inserting the mold only from theopening side of the inner diameter gradually-increasing portion 52 inthe axial direction of the venturi forming block 21. When the venturiportion 50 is subjected to the machining processing, this can beachieved by performing the machining processing only from the openingside of the inner diameter gradually-increasing portion 52 in the axialdirection of the venturi forming block 21. Therefore, manufacturabilityof the venturi portion 50 (the venturi forming block 21) can beimproved.

Third Embodiment

In the pump apparatus 1 according to a third embodiment, the pumphousing main body 20 is made from a metallic material similarly to thefirst embodiment. On the other hand, the venturi forming block 21 isalso made from a metallic material unlike the first embodiment. Morespecifically, the venturi forming block 21 is made from a sinteredmaterial. The venturi portion 50 is formed with use of a mold whenmetallic powder is molded by being compacted in a powder compactingprocess. This compact is sintered, by which the venturi forming block 21is formed.

If the pump apparatus 1 is configured in such a manner that the venturiforming block 21 is joined to the pump housing main body 20 (the venturiforming block containing hole 228 of the rear body 22), thisconfiguration can raise a problem such as occurrence of a distortionbetween the venturi forming block 21 and the pump housing main body 20after the venturi forming block 21 is joined to the pump housing mainbody 20. On the other hand, in the present embodiment, the venturiforming block 21 is made from the metallic material. Therefore, theventuri forming block 21 has a similar linear expansion coefficient tothe pump housing main body 20. Therefore, the present embodiment canprevent or reduce occurrence of a problem like the above-describedexample. Further, the venturi portion 50 (the inner diametergradually-increasing portion 52 and the like) is formed with use of themold. Therefore, the venturi portion 50 can be easily formed compared toforming the venturi portion 50 (the inner diameter gradually-increasingportion 52 and the like) by the machining processing.

Fourth Embodiment

The pump apparatus 1 according to a fourth embodiment is different fromthe first embodiment in terms of the layout of the venturi portion 50and the like. The fourth embodiment will be described below focusing ononly configurations different from the first embodiment. Configurationsshared with the first embodiment will be identified by the samereference numerals as the first embodiment, and descriptions thereofwill be omitted. FIG. 14 illustrates the pump housing 2 as viewed fromthe direction in which the driving shaft 40 (the central axis O) extends(as viewed from the negative side in the z-axis direction), and a partof an inner structure and contained components are indicated by brokenlines. FIG. 15 illustrates a cross section as viewed from a line B-Billustrated in FIG. 14. An orthogonal coordinate system is set in asimilar manner to the first embodiment (FIG. 3 and the like). The pumphousing 2 does not include the venturi forming block 21 like the firstembodiment. The pump housing main body 20 (the rear body 22) does notinclude the venturi forming block containing hole 228 like the firstembodiment. The inner diameter gradually-reducing portion 210 and theventuri portion 50 are directly formed inside the rear body 22.

The inner diameter gradually-reducing portion 210 and the venturiportion 50 extend in the z-axis direction on the positive side of therear body 22 in the x-axis direction and the negative side of the rearbody 22 in the y-axis direction. In other words, the longitudinaldirection of the venturi portion 50 extends generally in parallel withthe direction of the central axis O (the z-axis direction) and alsoextends perpendicularly to the longitudinal direction of the valvecontaining hole 227 (the x-axis direction). The venturi portion 50 doesnot overlap the containing recessed portion 220 in the directionperpendicular to the z axis (the radial direction of the rotational axisof the driving shaft 40) (the venturi portion 50 is located on theradially outer side with respect to the containing recessed portion220), but overlaps the containing recessed portion 220 in the z-axisdirection. The inner diameter gradually-reducing portion 210 includes afirst inner diameter gradually-reducing portion 210 a where a narrowerangle sandwiched between inner walls thereof is relatively large, and asecond inner diameter gradually-reducing portion 210 b where a narrowerangle thereof is relatively small. An end of the first inner diametergradually-reducing portion 210 a on the positive side in the z-axisdirection is opened on the surface of the rear body 22 on the positiveside in the z-axis direction. An inner diameter of the first innerdiameter gradually-reducing portion 210 a gradually reduces from thepositive side toward the negative side in the z-axis direction. An endof the second inner diameter gradually-reducing portion 210 b on thepositive side in the z-axis direction is connected to an end of thefirst inner diameter gradually-reducing portion 210 a on the negativeside in the z-axis direction. An inner diameter of the second innerdiameter gradually-reducing portion 210 b gradually reduces from thepositive side toward the negative side in the z-axis direction. An endof the small diameter portion 51 on the positive side in the z-axisdirection is connected to an end of the second inner diametergradually-reducing portion 210 b on the negative side in the z-axisdirection. An end of the small diameter portion 51 on the negative sidein the z-axis direction is connected to an end of the inner diametergradually-increasing portion 52 on the positive side in the z-axisdirection. The inner diameter of the inner diameter gradually-increasingportion 52 gradually increases from the positive side toward thenegative side in the z-axis direction. An end of the inner diametergradually-increasing portion 52 on the negative side in the z-axisdirection is opened on the surface of the rear body 22 on the negativeside in the z-axis direction.

The second hole 222 extends in the z-axis direction on the negative sideof the rear body 22 in the x-axis direction and the negative side of therear body 22 in the y-axis direction. An end of the second hole 222 onthe negative side in the z-axis direction is connected to an end of thefirst hole 221 on the negative side in the y-axis direction. An end ofthe second hole 222 on the positive side in the z-axis direction isopened on the surface of the rear body 22 on the positive side in thez-axis direction. The third hole 223 is formed inside the front body 24and is disposed so as to extend in the x-axis direction. An end of thethird hole 223 on the negative side in the x-axis direction is benttoward the negative side in the z-axis direction and opened on thesurface of the front body 24 on the negative side in the z-axisdirection, and is also connected to the end of the second hole 222 onthe positive side in the z-axis direction. An end of the third hole 223on the positive side in the x-axis direction is bent toward the negativeside in the z-axis direction and opened on the surface of the front body24 on the negative side in the z-axis direction, and is also connectedto the end of the first inner diameter gradually-reducing portion 210 aon the positive side in the z-axis direction. An inner diameter of theend of the first inner diameter gradually-reducing portion 210 a on thepositive side in the z-axis direction is approximately equal to an innerdiameter of the third hole 223. The fourth hole 224 connects the end ofthe valve containing hole 227 on the positive side in the x-axisdirection and the small diameter portion 51 of the venturi portion 50.

Next, functions and effects will be described. The pump housing 2 doesnot include the venturi forming block 21, and the inner diametergradually-reducing portion 210 and the venturi portion 50 are directlyformed inside the pump housing 2 (the rear body 22). Therefore, thepresent embodiment can reduce the number of components.

The venturi portion 50 should have a long dimension (a large space inthe longitudinal direction) compared to the orifice. On the other hand,the pump housing 2 has a dimension of the driving shaft 40 in therotational axis direction that is enough to contain the pump element 4therein from the beginning. In the present embodiment, the venturiportion 50 is disposed so as to be located on the radially outer sidewith respect to the pump element containing portion (the containingrecessed portion 220) and overlap the pump element containing portion(the containing recessed portion 220) in the direction of the rotationalaxis (the central axis O) of the driving shaft 40. The venturi portion50 is disposed so as to utilize the originally existing space extendingin the direction of the rotational axis of the driving shaft 40 in thismanner, by which the present embodiment can prevent or cut down theincrease in the size of the outer shape of the pump element 1 (in thedirection of the rotational axis of the driving shaft 40). Further, theventuri portion 50 is disposed in such a manner that the longitudinaldirection of the venturi portion 50 and the direction of the rotationalaxis (the central axis O) of the driving shaft 40 extend generally inparallel with each other. Therefore, the present embodiment can preventor cut down the increase in the dimension of the pump apparatus 1 in theradial direction of the rotational axis of the driving shaft 40. Thefunctions and effects due to the above-described layout can also beacquired even when the venturi portion 50 is formed in the venturiforming block 21.

Fifth Embodiment

The pump apparatus 1 according to a fifth embodiment is different fromthe first embodiment in terms of the housing where the venturi portion50 and the control valve 8 are set up. The fifth embodiment will bedescribed below focusing on only differences from the first embodiment.A transmission housing 10 a is a housing of the CVT unit, and is aseparate member from the pump housing 2. The pump housing 2 may bedisposed integrally with the transmission housing 10 a, or may be spacedapart from the transmission housing 10 a. While the pump element 4 isprovided in the pump housing 2, the venturi portion 50 and the controlvalve 8 are provided in the transmission housing (for example, a housingof the control valve) 10 a as indicated by a broken line illustrated inFIG. 1.

In this manner, the venturi portion 50 or the control valve 8 is notprovided on the pump housing 2 side but is provided on the transmissionhousing 10 a side, by which the present embodiment can reduce the sizeof the unit including the pump element 4 and improve layout flexibilitythereof. When the control valve 8 is provided on the transmissionhousing 10 a side, the hydraulic fluid supplied from the pump element 4(the pump housing 2) to the transmission housing 10 a is a flow amountbefore the hydraulic fluid is controlled by the control valve 8. Thecontrol valve 8 controls the flow amount of the hydraulic fluid to besupplied from the pump element 4 to the CVT 10. The above-described“flow amount of the hydraulic fluid to be supplied from the pump element4 to the CVT 10” means a flow amount to be actually supplied to the CVT10 existing inside the transmission housing 10 a. As indicated by analternate long and short dash line in FIG. 1, the venturi portion 50 maybe provided in the transmission housing 10 a, and the pump element 4 andthe control valve 8 may be provided in the pump housing 2. Further, theventuri portion 50 and the control valve 8 may be provided in a housingother than the transmission housing 10 a.

Sixth Embodiment

The pump element according to a sixth embodiment is a variabledisplacement pump in which the pump capacity is variably controlled. Thesixth embodiment will be described below focusing on only configurationsdifferent from the first embodiment. Configurations shared with thefirst embodiment will be identified by the same reference numerals asthe first embodiment, and descriptions thereof will be omitted. FIG. 16is a similar view to FIG. 2 that schematically illustrates aconfiguration of the pump apparatus 1. FIG. 17 illustrates a partialcross section acquired by cutting the pump housing 2 along the planeincluding the central axis O. The z axis is set to a horizontaldirection in FIG. 17, and a positive side thereof is set to a right sidein FIG. 17. The containing recessed portion 220, an intake pressurechamber 220 a, the discharge pressure chamber 226, the valve containinghole 227, the venturi forming block containing hole (not illustrated), abearing holding hole 229, and the plurality of passages 3 and the likeare formed in the rear body 22. The plurality of passages 3 and the likeinclude the intake passage 3, the discharge passage 5, the high pressurepassage 6, the intermediate pressure passage 7, a first control passage60, a second control passage 70, and the return passage 9. The intakepressure chamber 220 a and the discharge pressure chamber 226 are openedto the bottom portion of the containing recessed portion 220. A bush 401as a bearing is mounted on an inner periphery of the bearing holdinghole 229. The end of the valve containing hole 227 on the negative sidein the x-axis direction is opened on the outer surface of the rear body22. A solenoid 80 is fitted in this opening via a seal member 253. A rod800 protrudes from the solenoid 80 toward the positive side in thex-axis direction.

A shaft containing hole 234 is provided at the side plate 23. The intakeport 230, the discharge port 231, an intake-side backpressure port 232,and a discharge-side backpressure port 233 are provided at the surfaceof the side plate 23 on the one side in the axial direction. The intakeport 230 and the discharge port 231 are grooves extending in thecircumferential direction in a generally circular-arc manner, and areprovided at positions opposite of the shaft containing hole 234 fromeach other. The intake-side backpressure port 232 is a groove extendingin the circumferential direction in a generally circular-arc manner onone side closer to the shaft containing hole 234 (the radially innerside) with respect to the intake port 230, and is provided in a rangeoverlapping the intake port 230 in the circumferential direction. Thedischarge-side backpressure port 233 is a groove extending in thecircumferential direction in a generally circular-arc manner on theradially inner side with respect to the discharge port 231, and isprovided in a range overlapping the discharge port 231 in thecircumferential direction. The intake port 230 and the intake-sidebackpressure port 232 are connected to the intake pressure chamber 220 aof the rear body 22 via a communication passage in the side plate 23.The discharge port 231 and the discharge-side backpressure port 233 areconnected to the discharge pressure chamber 226 via a communicationpassage in the side plate 23. An annular seal groove is formed on thesurface of the side plate 23 on the negative side in the z-axisdirection so as to surround an outer edge of the side plate 23. Anannular seal member 250 is mounted in this seal groove. An annular sealgroove is formed on the surface of the bottom portion of the containingrecessed portion 220 on the positive side in the z-axis direction so asto surround an opening of the bearing holding hole 229. An annular sealmember 251 is mounted in this seal groove. An annular seal groove isformed on the surface of the bottom portion of the containing recessedportion 220 on the positive side in the z-axis direction so as tosurround an outer periphery of an opening of the discharge pressurechamber 226. An annular seal member 252 is mounted in this seal groove.The seal member 252 defines a high pressure region and a low pressureregion on an inner peripheral side and an outer peripheral side of theseal member 252, respectively.

A bush 402 as a bearing is mounted on an inner periphery of a bearingholding hole 244 of the front body 24. An intake port 240 and adischarge port 241, and an intake-side backpressure port 242 and adischarge-side backpressure port 243 are formed on the end surface ofthe front body 24 on the negative side in the z-axis direction atpositions generally corresponding in the z-axis direction to theindividual ports 230 and 231 and the individual ports 232 and 233 formedat the side plate 23 and with similar shapes to them, respectively. Thefront body 24 is fixed by being fastened to the rear body 22 with use ofa bolt 26.

An adapter ring 44 is mounted in the containing recessed portion 220 ofthe rear body 22 on the positive side of the side plate 23 in z-axisdirection. The adapter ring 44 has an annular shape, and an outerperiphery of the adapter ring 44 is fitted to the inner periphery of thecontaining recessed portion 220. An inner peripheral surface of theadapter ring 44 has a generally cylindrical shape extending in thez-axis direction and is generally ecliptic as viewed from the z-axisdirection. A first groove portion 441, a second groove portion 442, afirst flat surface portion 443, a second flat surface portion 444, and arecessed portion 445 are provided on this inner peripheral surface. Thefirst groove portion 441 has a semi-cylindrical shape extending in thez-axis direction, and is provided on the first flat surface portion 443.The first and second control passages 60 and 70 are provided on bothsides of the first groove portion 441 so as to radially penetratethrough the adapter ring 44. The second groove portion 442 is providedon an opposite side of a center (a central axis) of the adapter ring 44from the first groove portion 441, and extends in the z-axis direction.The second flat surface portion 444 is provided between the first andsecond groove portions 441 and 442 (a generally middle positiontherebetween) in a circumferential direction of the adapter ring 44. Therecessed portion 445 is provided on an opposite side of the center ofthe adapter ring 44 from the second flat surface portion 444.

The pump element 4 is contained in a space surrounded by an innerperipheral surface of the adapter ring 44, the surface of the side plate23 on the positive side in the z-axis direction, and the surface of thefront body 24 on the negative side in the z-axis direction. In otherwords, the above-described space functions as the pump elementcontaining portion. Eleven slits 410 are provided at the rotor 41. Thecam ring 43 is annularly formed, and the inner peripheral surfacethereof has a generally cylindrical shape. A semi-cylindrical grooveportion 433 extending in the z-axis direction is provided on an outerperipheral surface of the cam ring 43. The cam ring 43 is provided inthe pump element containing portion so as to surround the rotor 41. Thecam ring 43 forms the plurality of pump chambers 400 together with therotor 41 and the vanes 42. In other words, the side plate 23 and thefront body 24 are disposed on the side surfaces of the cam ring 43 andthe rotor 41 in the axial direction. The space between the innerperipheral surface of the cam ring 43 and the outer peripheral surfaceof the rotor 41 is sealingly closed on the both sides thereof in theaxial direction by the side plate 23 and the front body 24, while beingdivided into the eleven pump chambers 400 by the plurality of vanes 42.

The cam ring 43 is provided displaceably in the pump element containingportion. A pin 453 is installed by being fitted between the first grooveportion 441 of the adapter ring 44 and the groove portion 433 of the camring 43. The pin 453 is fixed to the pump housing 2. The pin 453prevents or reduces a rotation of the adapter ring 44 relative to thepump housing 2 and also prevents or reduces a rotation of the cam ring43 relative to the adapter ring 44. The cam ring 43 is contained on theinner peripheral side of the adapter ring 44 swingably relative to thepump housing 2. The cam ring 43 is supported on the first flat surfaceportion 443 relative to the adapter ring 44. The cam ring 43 swings withthe first flat surface portion 443 serving as a supporting point thereofby being displaced while rolling on the first flat surface portion 443.Hereinafter, an amount by which a center (a central axis) of the innerperipheral surface of the cam ring 43 is offset from the center (thecentral axis O) of the rotor 41 (the driving shaft 40) will be referredto as an eccentric amount 5.

A seal member 46 is mounted in the second groove portion 442 of theadapter ring 44. When the cam ring 43 swings, the first flat surfaceportion 443 of the adapter ring 44 contacts the outer peripheral surfaceof the cam ring 43 and the seal member 46 also contacts the outerperipheral surface of the cam ring 43. The above-described space betweenthe inner peripheral surface of the adapter ring 44 and the outerperipheral surface of the cam ring 43 is liquid-tightly divided into apair of spaces by the first flat surface portion 443 (a portion thereofin abutment with the outer peripheral surface of the cam ring 43) andthe seal member 46. In other words, two fluid pressure chambers 61 and71 are formed as the pair of spaces between the cam ring 43 and the pumpelement containing portion. For convenience of the description, an Xaxis and a Y axis are set to a long-axis direction and a short-axisdirection of the generally ecliptic inner peripheral surface of theadapter ring 44, respectively, as illustrated in FIG. 16. On the outerperipheral side of the cam ring 43, a first fluid pressure chamber 61 isdefined on the negative side in the X-axis direction that is one sidewhere the eccentric amount δ increases, and a second fluid pressurechamber 71 is defined on the positive side in the X-axis direction thatis the other side where δ reduces. When δ increases, a volume of thefirst fluid pressure chamber 61 reduces and a volume of the second fluidpressure chamber 71 increases. One end of a spring 47 is set in therecessed portion 445 of the adapter ring 44 inside the second fluidpressure chamber 71. The other end of the spring 47 is set on the outerperipheral side of the cam ring 43. The spring 47 is mounted in acompressed state, and constantly biases the cam ring 43 relative to theadapter ring 44 toward the negative side in the X-axis direction (theone side where the first fluid pressure chamber 61 is located). Thedisplacement of the cam ring 43 toward the negative side in the X-axisdirection is regulated by abutment of the outer peripheral surface ofthe cam ring 43 with the second flat surface portion 444 of the adapterring 44 inside the first fluid pressure chamber 61.

The rotor 41 rotates in a clockwise direction in FIG. 16. With thecenter of the cam ring 43 located eccentrically from the central axis O(toward the negative side in the X-axis direction), a radial distancebetween the outer peripheral surface of the rotor 41 and the innerperipheral surface of the cam ring 43 (a radial dimension of the pumpchamber 400) increases as approaching the negative side in the X-axisdirection from the positive side in the X-axis direction. The vane 42projects from the slit 410 and retracts into the slit 410 according tothis change in the distance, by which each of the pump chamber 400 isdefined. The volume of the pump chamber 400 on the negative side in theX-axis direction becomes larger than the volume of the pump chamber 400on the positive side in the X-axis direction. Due to this difference inthe volume of the pump chamber 400, the volume of the pump chamber 400reduces as the rotor 41 rotates (as the pump chamber 400 travels towardthe positive side in the X-axis direction) on the positive side in theY-axis direction with respect to the central axis O, while increasing asthe rotor 41 rotates (as the pump chamber 400 travels toward thenegative side in the X-axis direction) on the negative side in theY-axis direction with respect to the central axis O. The pump chamber400 periodically expands and contracts while rotating in the clockwisedirection around the central axis O. The intake port 230 is opened tothe intake region where the volume of the pump chamber 400 increasesaccording to the rotation of the driving shaft 40. The discharge port231 is opened to the discharge region where the volume of the pumpchamber 400 reduces according to the rotation of the driving shaft 40.

The intake passage 3 connects the oil pan 100 and the intake pressurechamber 220 a to each other. The discharge passage 5 connects thedischarge pressure chamber 226 and the CVT 10 to each other. The highpressure passage 6 branches off from the discharge passage 5 on theupstream side of the venturi portion 50 in the discharge passage 5, andis connected to the positive side of the valve containing hole 227 inthe x-axis direction. The intermediate pressure passage 7 branches offfrom the venturi portion 50 (the small diameter portion 51) in thedischarge passage 5 and is connected to the negative side of the valvecontaining hole 227 in the x-axis direction. The first control passage60 and the second control passage 70 connect the control valve 8 and thepump element 4 to each other. The first control passage 60 is connectedto the positive side of the valve containing hole 227 in the x-axisdirection with respect to the high pressure passage 6, and is alsoconnected to the first fluid pressure chamber 61 by penetrating throughthe adapter ring 44. The second control passage 70 is connected to thenegative side of the valve containing hole 227 in the x-axis directionwith respect to the intermediate pressure passage 7, and is alsoconnected to the second fluid pressure chamber 71 by penetrating throughthe adapter ring 44. The return passage 9 is connected to between thefirst control passage 60 and the second control passage 70 in the valvecontaining hole 227. Regardless of the displacement of the control valve8 inside the valve containing hole 227, the high pressure passage 6 isopened to the high pressure chamber 86, the intermediate pressurepassage 7 is opened to the intermediate pressure chamber 88, and thereturn passage 9 is opened to the drain chamber 89.

The control valve 8 switches the flow passage of the hydraulic fluidbetween the first control passage 60 and the second control passage 70.In an initial state where the control valve 8 is maximally displacedtoward the negative side in the x-axis direction, an opening portion ofthe first control passage 60 in the valve containing hole 227 is incommunication with the drain chamber 89 while being out of communicationwith the high pressure chamber 86 due to the first land portion 8. Inthe same initial state, an opening portion of the second control passage70 is in communication with the intermediate pressure chamber 88 whilebeing out of communication with the drain chamber 89 due to the secondland portion 82. As a result, the hydraulic fluid in the intermediatepressure chamber 88 flows into the second fluid pressure chamber 71. Thehigh pressure is not supplied into the first fluid pressure chamber 61and the intermediate pressure is supplied into the second fluid pressurechamber 71, so that the cam ring 43 is displaced into an eccentricstate. Therefore, the pump discharge flow amount increases according tothe number of rotations. With the control valve 8 displaced toward thepositive side in the x-axis direction by a predetermined amount or more,the opening portion of the first control passage 60 is in communicationwith the high pressure chamber 86 while being out of communication withthe drain chamber 89 due to the first land portion 81. In the samestate, the opening portion of the second control passage 70 is incommunication with the drain chamber 89 while being out of communicationwith the intermediate pressure chamber 88 due to the second land portion82. As a result, the flow passage is switched, so that the hydraulicfluid in the high pressure chamber 86 starts to flow into the firstfluid pressure chamber 61 via the first control passage 60. The highpressure is supplied into the first fluid pressure chamber 61, and theintermediate pressure is not supplied into the second fluid pressurechamber 71. Therefore, the eccentric amount δ of the cam ring 43 reducesand the pump capacity reduces, so that the pump discharge flow amountdoes not increase even when the number of rotations of the pumpincreases. In other words, the control valve 8 switches the flow passagein such a manner that the hydraulic fluid introduced via the highpressure passage 6 is introduced into the first fluid pressure chamber61 based on the differential pressure Δp between the upstream side andthe small diameter portion 51 of the venturi portion 50. When thehydraulic fluid starts to be introduced into the first fluid pressurechamber 61, the flow amount to be supplied to the CVT 10 via thedischarge passage 5 is limited to a required amount. In this manner, theventuri portion 50, the high pressure passage 6, the intermediatepressure passage 7, the control valve 8, the first control passage 60,the second control passage 70, the first fluid pressure chamber 61, andthe second fluid pressure chamber 71 function as a controller thatcontrols the discharge flow amount of the pump element 4.

The activation of the control valve 8 is controlled based on thedifferential pressure Δp applied to the both sides of the control valve8 in the axial direction according to the discharge flow amount of thepump element 4, and is also controlled based on a thrust force appliedfrom the solenoid 80 to the control valve 8. In other words, a distalend of the rod 800 of the solenoid 80 is in abutment with the endsurface of the control valve 8 on the negative side in the x-axisdirection. The rod 800 is displaceable in the x-axis direction due to anelectromagnetic force generated by the solenoid 80. The control valve 8is subjected to a force F4 applied from the solenoid 80 toward thepositive side in the x-axis direction via the rod 800. The thrust forceF4 of the solenoid 80 is controlled based on an instruction from the CVTcontrol unit. When a sum of the difference between F1 and F2, i.e.,F1−F2 (the force corresponding to the differential pressure Δp) and F4(F1−F2+F4) exceeds F3, the control valve 8 is displaced toward thepositive side in the x-axis direction. With the solenoid 80 deactivated,the force competing against the initial set load F3 of the spring 88 isonly the force F1−F2 due to the differential pressure Δp. On the otherhand, the differential pressure Δp (i.e., F1−F2) cannot be sufficientlysecured until the discharge flow amount increases to some degree. Thisleads to such an operation of maintaining a certain flow amount afterachieving a relatively large discharge flow amount. Generating F4 bysupplying power to the solenoid 80 can bring about the same effect aschanging the initial set load F3 of the spring 88 to a lower load. Inother words, this configuration allows the control valve 8 to bedisplaced and switch the flow passage with the relatively smalldifferential pressure Δp (i.e., F1−F2). Therefore, this configurationleads to such an operation of maintaining a certain flow amount afterachieving a relatively small discharge flow amount. In this manner, thepresent embodiment can control the discharge flow amount with use of amagnetic attractive force (the thrust force F4) generated by thesolenoid 80. The CVT control unit appropriately controls a line pressureof the CVT 10 according to running conditions such as the number ofrevolutions of the engine, an opening degree of an accelerator (anopening degree of a throttle valve), and a vehicle speed. Accordingthereto, the CVT control unit supplies a current to the solenoid 80based on the number of revolutions of the engine, the opening degree ofthe accelerator, and the like to control the magnetic attractive force(the thrust force F4), thereby changing the discharge flow amount (thepump capacity) of the pump element 4. The pump apparatus 1 may beconfigured to omit the solenoid 80.

The present embodiment can also acquire each of functions and effectsregarding the venturi portion 50 similar to the first embodiment evenfor the variable displacement pump.

Other Embodiments

Having described the pump apparatus according to the present inventionbased on the embodiments thereof, the specific configuration of thepresent invention is not limited to the embodiments, and the presentinvention also includes a design modification and the like thereof madewithin a range that does not depart from the spirit of the presentinvention. For example, the stepless transmission to which the pumpapparatus supplies the hydraulic fluid is not limited to the CVT, andmay be, for example, a toroidal-type transmission. The automatictransmission to which the pump apparatus supplies the hydraulic fluid isnot limited to the stepless transmission, and may be a steppedtransmission. The apparatus mounted on the vehicle to which the pumpapparatus supplies the hydraulic fluid is not limited to the automatictransmission, and may be a power steering apparatus or the like.Further, the configurations of the individual embodiments can also bearbitrarily combined to each other or one another.

The present application claims priority to Japanese Patent ApplicationNo. 2015-004311 filed on Jan. 13, 2015. The entire disclosure ofJapanese Patent Application 2015-004311 filed on Jan. 13, 2015 includingthe specification, the claims, the drawings, and the abstract isincorporated herein by reference in its entirety.

REFERENCE SIGNS LIST

1 pump apparatus

10 CVT (automatic transmission)

2 pump housing

20 pump housing main body

21 venturi forming block

213 communication hole (opening)

230 intake port

231 discharge port

4 pump element

40 driving shaft

400 pump chamber

41 rotor

410 slit

42 vane

43 cam ring

5 discharge passage

50 venturi portion

51 small diameter portion

52 inner diameter gradually-increasing portion

520 front portion

521 rear portion

53 large diameter portion

61 first fluid pressure chamber

71 second fluid pressure chamber

8 control valve

86 high pressure chamber

87 intermediate pressure chamber

1. An automatic transmission pump apparatus for supplying hydraulic fluid to an automatic transmission of a vehicle, the automatic transmission pump apparatus comprising: a pump housing including a pump element containing portion; a driving shaft pivotally supported on the pump housing; a pump element provided in the pump element containing portion and configured to be rotationally driven by the driving shaft, the pump element forming a plurality of pump chambers around the driving shaft; an intake port formed at the pump housing and opened to an intake region where a volume of a pump chamber increases according to a rotation of the driving shaft among the plurality of pump chambers; a discharge port formed at the pump housing and opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers; a discharge passage connected to the discharge port; and a venturi portion provided on the way along the discharge passage, the venturi portion including a small diameter portion having a smaller inner diameter than an inner diameter of the discharge passage from the discharge port to the venturi portion and an inner diameter gradually-increasing portion formed in such a manner that an inner diameter thereof gradually increases from the small diameter portion toward a downstream side of the discharge passage; and a control valve configured to receive introduction of hydraulic fluid on an upstream side of the venturi portion and hydraulic fluid in the venturi portion, the control valve including a spool valve body controlled based on a differential pressure between the hydraulic fluid on the upstream side of the venturi portion and the hydraulic fluid in the venturi portion, the control valve being configured to control a flow amount of the hydraulic fluid to be supplied into the automatic transmission at least by switching a flow passage of the hydraulic fluid introduced from the upstream side of the venturi portion.
 2. The automatic transmission pump apparatus according to claim 1, wherein the pump housing includes a pump housing main body including the pump element containing portion, and a venturi forming block that is a separate member from the pump housing main body and is joined to the pump housing main body, wherein the venturi portion is formed at the venturi forming block, and wherein the venturi forming block is jointed to the pump housing main body after the venturi portion is formed.
 3. The automatic transmission pump apparatus according to claim 2, wherein the pump housing main body is made from a metallic material, wherein the venturi forming block is made from a resin material, and wherein the venturi portion is formed by molding.
 4. The automatic transmission pump apparatus according to claim 2, wherein the pump housing main body is made from a metallic material, wherein the venturi forming block is made from a sintered material, and wherein the venturi portion is formed with use of a mold in a powder compacting process.
 5. The automatic transmission pump apparatus according to claim 2, wherein the small diameter portion of the venturi portion is formed so as to be opened on an outer surface of the venturi forming block.
 6. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion is provided in such a manner that a longitudinal direction of the venturi portion and a direction of a, rotational axis of the driving shaft extend generally perpendicularly to each other.
 7. The automatic transmission pump apparatus according to claim 6, wherein the venturi portion is provided at a position that does not overlap the intake port on a cross section perpendicular to the rotational axis of the driving shaft but overlaps the intake port in the direction of the rotational axis of the driving shaft.
 8. The automatic transmission pump apparatus according to claim 6, wherein the venturi portion is provided in such a manner that a longitudinal direction of the venturi portion and a longitudinal direction of the control valve extend generally in parallel with each other.
 9. The automatic transmission pump apparatus according to claim 8, wherein the control valve includes a high pressure chamber into which a pressure on the upstream side of the venturi portion is introduced and an intermediate pressure chamber into which a pressure in the venturi portion is introduced, and wherein the venturi portion is disposed in such a manner that the upstream side of the venturi portion faces the high pressure chamber of the control valve.
 10. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion is provided in such a manner that a longitudinal direction of the venturi portion and a direction of a rotational axis of the driving shaft extend generally in parallel with each other.
 11. The automatic transmission pump apparatus according to claim 10, wherein the venturi portion is provided at a position that is located on a radially outer side with respect to the pump element containing portion in a radial direction of the rotational axis of the driving shaft, and overlaps the pump element containing portion in the direction of the rotational axis of the driving shaft.
 12. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion includes an opening provided on the small diameter portion or one side of the inner diameter gradually-increasing portion that is closer to the small diameter portion in a longitudinal direction of the venturi portion, the opening being configured to supply the hydraulic fluid in the venturi portion into the control valve, and wherein the opening includes a plurality of openings provided in a direction around an axis line along the longitudinal direction of the venturi portion.
 13. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion is formed in such a manner that a narrower angle sandwiched between inner walls of the inner diameter gradually-increasing portion is 60 degrees or smaller.
 14. The automatic transmission pump apparatus according to claim 13, wherein, when it is defined that L represents a length of a longitudinal direction of the inner diameter gradually-increasing portion when the inner diameter gradually-increasing portion is formed as far as an inner diameter thereof reaches a same diameter as an inner diameter of the discharge passage from the discharge port to the venturi portion while the narrower angle sandwiched between inner walls of the inner diameter gradually-increasing portion is kept constant, the inner diameter gradually-increasing portion includes a front portion formed as far as a position where the length in the longitudinal direction is 65% of the length L or longer while the narrower angle sandwiched between the inner walls of the inner diameter gradually-increasing portion is kept constant at 60 degrees or smaller, and a rear portion provided on a downstream side of the front portion and formed in such a manner that the narrower angle exceeds 60 degrees.
 15. The automatic transmission pump apparatus according to claim 1, wherein the control valve or the venturi portion is provided at a housing that is a separate member from the pump housing.
 16. The automatic transmission pump apparatus according to claim 1, wherein the venturi portion includes an opening provided at the small diameter portion and configured to supply the hydraulic fluid in the venturi portion to the control valve.
 17. The automatic transmission pump apparatus according to claim 1, wherein the pump element is a pump element for a fixed displacement pump in which a discharge amount per rotation of the driving shaft is constant, and wherein the control valve switches the flow passage of the hydraulic fluid so as to return the hydraulic fluid introduced from the upstream side of the venturi portion to an intake port side.
 18. The automatic transmission pump apparatus according to claim 1, wherein the pump element includes a rotor including a plurality of slits in a circumferential direction, a vane provided so as to be projectable and retractable from and into each of the slits of the rotor, a cam ring provided displaceably in the pump element containing portion and annularly formed, the cam ring forming the plurality of pump chambers together with the rotor and the vane, and a first fluid pressure chamber and a second fluid pressure chamber that are a pair of spaces formed between the cam ring and the pump element containing portion, the first fluid pressure chamber and the second fluid pressure chamber being respectively provided on one side where a volume reduces and an opposite side where the volume increases when an eccentric amount of the cam ring with respect to the rotor increases, wherein the pump element is a pump element of a variable displacement pump in which a discharge amount per rotation of the driving shaft is variably controlled, and wherein the control valve switches the flow passage of the hydraulic fluid so as to introduce the hydraulic fluid introduced from the upstream side of the venturi portion into the first fluid pressure chamber.
 19. A pump apparatus comprising: a pump housing including a pump element containing portion; a driving shaft pivotally supported on the pump housing; a pump element provided in the pump element containing portion and configured to be rotationally driven by the driving shaft, the pump element forming a plurality of pump chambers around the driving shaft; an intake port formed at the pump housing and opened to an intake region where a volume of a pump chamber increases according to a rotation of the driving shaft among the plurality of pump chambers; a discharge port formed at the pump housing and opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers; a discharge passage connected to the discharge port; and a venturi portion provided on the way along the discharge passage, the venturi portion including a small diameter portion having a smaller inner diameter than an inner diameter of the discharge passage from the discharge port to the venturi portion and an inner diameter gradually-increasing portion formed in such a manner that an inner diameter thereof gradually increases from the small diameter portion toward a downstream side of the discharge passage; and a control valve configured to receive introduction of hydraulic fluid on an upstream side of the venturi portion and hydraulic fluid in the small diameter portion, the control valve including a spool valve body controlled based on a differential pressure between the hydraulic fluid on the upstream side of the venturi portion and the hydraulic fluid in the small diameter portion, the control valve being configured to control a flow amount of the hydraulic fluid to be supplied into an apparatus mounted on a vehicle at least by switching a flow passage of the hydraulic fluid introduced from the upstream side of the venturi portion. 